From 9e711f5c9c18db7f0c62cb103d4bb84ead101de2 Mon Sep 17 00:00:00 2001
From: Hideki Miyazaki <hide@wolfssl.com>
Date: Thu, 4 Jun 2026 09:08:24 +0900
Subject: [PATCH] Add MAX ENTROPY BITS check

---
 tests/api/test_random.c     | 30 ++++++++++++++++++++++++++++++
 tests/api/test_random.h     |  4 +++-
 wolfcrypt/src/wolfentropy.c |  2 +-
 3 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/tests/api/test_random.c b/tests/api/test_random.c
index cdd7e84499..85ce701283 100644
--- a/tests/api/test_random.c
+++ b/tests/api/test_random.c
@@ -30,6 +30,9 @@
 
 #include <wolfssl/wolfcrypt/random.h>
 #include <wolfssl/wolfcrypt/types.h>
+#ifdef HAVE_ENTROPY_MEMUSE
+    #include <wolfssl/wolfcrypt/wolfentropy.h>
+#endif
 #include <tests/api/api.h>
 #include <tests/api/test_random.h>
 
@@ -739,3 +742,30 @@ int test_wc_RNG_HealthTest_SHA512(void)
     return EXPECT_RESULT();
 }
 
+int test_wc_Entropy_Get(void)
+{
+    EXPECT_DECLS;
+#ifdef HAVE_ENTROPY_MEMUSE
+    byte entropy[WC_SHA3_256_DIGEST_SIZE]; /* 32 bytes */
+
+    /* bits <= 0: must reject */
+    ExpectIntEQ(wc_Entropy_Get(0, entropy, sizeof(entropy)),
+        WC_NO_ERR_TRACE(BAD_FUNC_ARG));
+    ExpectIntEQ(wc_Entropy_Get(-1, entropy, sizeof(entropy)),
+        WC_NO_ERR_TRACE(BAD_FUNC_ARG));
+
+    /* bits > MAX_ENTROPY_BITS: must reject (overflow guard) */
+    ExpectIntEQ(wc_Entropy_Get(MAX_ENTROPY_BITS + 1, entropy, sizeof(entropy)),
+        WC_NO_ERR_TRACE(BAD_FUNC_ARG));
+    ExpectIntEQ(wc_Entropy_Get(2049, entropy, sizeof(entropy)),
+        WC_NO_ERR_TRACE(BAD_FUNC_ARG));
+
+    /* entropy == NULL with len > 0: must reject */
+    ExpectIntEQ(wc_Entropy_Get(MAX_ENTROPY_BITS, NULL, sizeof(entropy)),
+        WC_NO_ERR_TRACE(BAD_FUNC_ARG));
+
+    /* valid call: bits == MAX_ENTROPY_BITS */
+    ExpectIntEQ(wc_Entropy_Get(MAX_ENTROPY_BITS, entropy, sizeof(entropy)), 0);
+#endif /* HAVE_ENTROPY_MEMUSE */
+    return EXPECT_RESULT();
+}
diff --git a/tests/api/test_random.h b/tests/api/test_random.h
index 0f41b3e04a..07a86e6904 100644
--- a/tests/api/test_random.h
+++ b/tests/api/test_random.h
@@ -37,6 +37,7 @@ int test_wc_RNG_DRBG_Reseed(void);
 int test_wc_RNG_TestSeed(void);
 int test_wc_RNG_HealthTest(void);
 int test_wc_RNG_HealthTest_SHA512(void);
+int test_wc_Entropy_Get(void);
 
 #define TEST_RANDOM_DECLS                                           \
     TEST_DECL_GROUP("random", test_wc_InitRng),                     \
@@ -51,6 +52,7 @@ int test_wc_RNG_HealthTest_SHA512(void);
     TEST_DECL_GROUP("random", test_wc_RNG_DRBG_Reseed),             \
     TEST_DECL_GROUP("random", test_wc_RNG_TestSeed),                \
     TEST_DECL_GROUP("random", test_wc_RNG_HealthTest),              \
-    TEST_DECL_GROUP("random", test_wc_RNG_HealthTest_SHA512)
+    TEST_DECL_GROUP("random", test_wc_RNG_HealthTest_SHA512),       \
+    TEST_DECL_GROUP("random", test_wc_Entropy_Get)
 
 #endif /* WOLFCRYPT_TEST_RANDOM_H */
diff --git a/wolfcrypt/src/wolfentropy.c b/wolfcrypt/src/wolfentropy.c
index a8f42119f6..1d23c7d8c2 100644
--- a/wolfcrypt/src/wolfentropy.c
+++ b/wolfcrypt/src/wolfentropy.c
@@ -816,7 +816,7 @@ int wc_Entropy_Get(int bits, unsigned char* entropy, word32 len)
     int noise_len;
     static byte noise[MAX_NOISE_CNT];
 
-    if (bits <= 0 || (entropy == NULL && len > 0)) {
+    if (bits <= 0 || bits > MAX_ENTROPY_BITS || (entropy == NULL && len > 0)) {
         return BAD_FUNC_ARG;
     }